% A simple Tree
% Author: Stefan Kottwitz
% https://www.packtpub.com/hardware-and-creative/latex-cookbook
\documentclass[border=10pt]{standalone} 
%%%<
\usepackage{verbatim}
%%%>
\begin{comment}
:Title: A simple Tree
:Tags: Trees;Cookbook
:Author: Stefan Kottwitz
:Slug: tree

A simple tree with a style for all nodes.
\end{comment}

\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[%sibling distance=25em,
  every node/.style = {shape=rectangle, rounded corners,
    draw, align=center,
    top color=white, bottom color=blue!20},
  level 1/.style={sibling distance=10em},
  level 2/.style={sibling distance=5em}]
  \node {A}
    child { node {B} }
    child { node {C} }
    child { node {D}
      child { node {H} } }
    child {node {E}
      child {node {I} }
      child {node {J} 
        child {node {P} }
        child {node {Q} } } }
    child { node {F} 
      child {node {K} }
      child {node {L} }
      child {node {M} } }
    child {node {G} 
      child {node {N} } };
\end{tikzpicture}
\end{document}